/*
 * Perform chroot, set uid and gid, and then run prog
 *
 * Usage: chroot+setuidgid [--chroot chrootdir] [--setuidgid uid gid] prog [prog_args...]
 *
 * Alternatively, chrootdir, uid, gid, and prog can be compiled in
 * by defining macros for CHROOTDIR, UID, GID, PROG
 *
 * R. Perry, Jan. 2003
 *
 * 29 Aug. 2003, added --stdout option to redirect stdout to a file after setting chroot and uidgid
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>
#include <grp.h>

int putenv(char *string);

int main( int argc, char *argv[])
{
    char *progname = argv[0];

    char *chrootdir;

    uid_t uid;
    gid_t gid;
    gid_t grouplist[1];

    char *prog;
    char **args;

/*** Must be the first command-line option: --chroot chrootdir ***/

#ifdef CHROOTDIR
	chrootdir = CHROOTDIR;
#else
    if( argc >= 3 && strcmp( argv[1], "--chroot") == 0)
    {
	chrootdir = argv[2];
#endif
	if( chroot( chrootdir))
	{
	    fprintf( stderr, "%s: chroot(\"%s\") failed: %s\n", progname, chrootdir, strerror(errno));
	    exit(1);
	}

	if( chdir( "/"))
	{
	    fprintf( stderr, "%s: chdir(\"/\") failed: %s\n", progname, strerror(errno));
	    exit(1);
	}

#ifndef CHROOTDIR
	argc -= 2;
	argv += 2;
    }
#endif

/*** Must be the first command-line option: --setuidgid uid gid ***/

#ifdef UID
	uid = UID;
	gid = GID;
#else
    if( argc >= 4 && strcmp( argv[1], "--setuidgid") == 0)
    {
	uid = atoi( argv[2]);
	gid = atoi( argv[3]);
#endif

	grouplist[0] = gid;

	if( setgroups( 1, grouplist))
	{
	    fprintf( stderr, "%s: setgroups() failed: %s\n", progname, strerror(errno));
	    exit(1);
	}

	if( setgid( gid))
	{
	    fprintf( stderr, "%s: setgid() failed: %s\n", progname, strerror(errno));
	    exit(1);
	}

	if( setuid( uid))
	{
	    fprintf( stderr, "%s: setuid() failed: %s\n", progname, strerror(errno));
	    exit(1);
	}

#ifndef UID
	argc -= 3;
	argv += 3;
    }
#endif

#ifdef STDOUT

/*** Must be the first command-line option: --stdout file ***/

    if( argc >= 3 && strcmp( argv[1], "--stdout") == 0)
    {
	char *outfile = argv[2];

	if( freopen( outfile, "w", stdout) == NULL)
	{
	    fprintf( stderr, "%s: freopen(\"%s\") failed: %s\n", progname, outfile, strerror(errno));
	    exit(1);
	}

	argc -= 2;
	argv += 2;
    }

#endif /* STDOUT */

/*** exec prog ***/

#ifdef PROG
    prog = PROG;
    args = argv;
#else
    if( argc < 2)
    {
	fprintf( stderr, "Usage: %s [--chroot chrootdir] [--setuidgid uid gid]"
#ifdef STDOUT
	  " [--stdout outfile]"
#endif
	  " prog [prog_args...]\n", progname);
	exit(1);
    }

    prog = argv[1];
    args = argv+1;
#endif

#ifdef PUTENV_COURSE
{
    char *val, course[1024];

    val = strrchr( progname, '/');
    val = val ? val+1 : progname;

    strcpy( course, "COURSE=");
    strncat( course, val, 1024-10);

    if( putenv( course) )
	fprintf( stderr, "%s: putenv(\"%s\") failed: %s\n", progname, course, strerror(errno));
}
#endif

    execv( prog, args);

    /* if execv() returns, it failed */

    fprintf( stderr, "%s: execv(\"%s\") failed: %s\n", progname, prog, strerror(errno));

    exit(1);
}